Issue #3273317 by clayfreeman, larowlan, tim.plunkett, danflanagan8: Add 'in_preview' variable to block and layout templates

Issue #3027653 by clayfreeman, tim.plunkett, Pavel Ruban, raman.b, ankithashetty, cboyden, larowlan, mpotter, phenaproxima: Allow block and layout plugins to determine if they are being previewed

Issue #3115503 by clayfreeman, tim.plunkett, alexpott, andypost: Support context aware layout plugins

Issue #3073872 by tim.plunkett, starshaped, webchick, phenaproxima, worldlinemine, AaronMcHale, jrockowitz, ckrina: Allow for Layout Builder sections to be given administrative labels

Revert "Issue #2852463 by mikelutz, tim.plunkett, heddn, xjm, MegaChriz, joachim, phenaproxima, dawehner, benjifisher: Create a trait to implement \Drupal\Component\Plugin\ConfigurableInterface"

This reverts commit 109dfd58.

Issue #2852463 by mikelutz, tim.plunkett, heddn, xjm, MegaChriz, joachim, phenaproxima, dawehner, benjifisher: Create a trait to implement \Drupal\Component\Plugin\ConfigurableInterface

Issue #2834025 by tim.plunkett, Manuel Garcia, swentel, japerry: Mark Layout Discovery as a stable module

Issue #2851648 by tim.plunkett, jibran: Layout regions should be in the order defined by the definition

Issue #2296423 by tim.plunkett, dsnopek, swentel, Manuel Garcia, tedbow, alexpott, xjm, andypost, dawehner, effulgentsia, Berdir, jhedstrom, catch, benjy, jibran, Wim Leers, tstoeckler, larowlan, webchick: Implement layout plugin type in core